IHC Receiver

[musketjon]

On page 20 of the GCA Journal, Volume 23, Issue 2, Spring 2009, the top 2 pics show the typical IHC/IHC and SA/IHC and HRA/IHC curved vs. straight line machining. I have an ordinary IHC/IHC PS receiver and it is straight cut, not even a hint of the curve. Did IHC do it right once in a while or do I have some kind of a rarity here? Just curious, that's all.
Jon
http://i660.photobucket.com/albums/uu321/musketjon/IMG_0002-10.jpg
http://i660.photobucket.com/albums/uu321/musketjon/IMG_0001.jpg